1. Field of the Invention
The present disclosure relates to a system and method for examining and testing solid objects using non-destructive ultrasonic phased arrays. More particularly, the present disclosure relates to a system and method for examining and testing seamless mechanical tubing and piping.
2. Background Art
Solid objects such as mechanical equipment may sometimes have physical flaws. Flaws may either occur during the manufacturing stage or at a later time due to external factors. It is important to find such flaws prior to the mechanical equipment being put into use. Otherwise, the mechanical equipment may fail causing loss of property or personal injury. However, such flaws are often undetectable via visual inspection. Thus, there is a need for a method which may be used to detect such flaws so that they may be detected in a timely manner and problems prevented.
Much of the tubular steel used in the petrochemical industry is inspected using a process commonly referred to as A-scan examination. In the A-scan examination process, ultrasonic waves are introduced into the outer surface of the pipe at a prescribed angle. Pulses of sound are introduced into the part being inspected through a probe containing a single crystal element (i.e., monocrystal), referred to as a transducer. Then, the echo returned is analyzed. The return echo is a function of the geometry of the material. When there is a flaw, the geometry of the material is internally changed, which is indicated by the return echo of the A-scan examination process. However, if the flaw in the material is not generally perpendicular to the sound path, the flaw may go undetected.
To control the direction of the sound, a plastic wedge is fastened to the face of the transducer, which is then connected to the ultrasonic flaw detector via coaxial cable. This wedge is formed at an angle so that the sound enters the steel at that specific angle. The angle used in the A-scan examination process is typically a 45 degree angle. However, a single 45 degree angle cannot detect all of the flaws due to geometry aspects of the ultrasonic waves. For example, if a flaw in the pipe is itself angled at 45 degrees, the A-scan examination process will not detect it.
The traditional A-scan flaw detectors cannot electronically control the angle at which the sound is projected. The angle of sound cannot be changed without removing the wedge and replacing it with another wedge that has a different angular relationship between the ultrasonic wave and the structure being measured.
Weld joints may be particularly problematic. Welds are known to be subject to many types of defects that can orient themselves in unpredictable ways. Accordingly, weld inspections are generally more rigorous and meticulous than inspections performed on raw materials, such as tubing.
Phased Array Ultrasonic Testing (“PAUT”) is a newer technology that is being used in a variety of industries to verify the integrity of welds. A PAUT scan is typically referred to as an “S-scan.”
Unlike an A-scan flaw detector that uses a single-element transducer, a phased array system uses transducers with multiple emission elements (i.e., 8, 16, 32, 64, 128, etc.) to create sound waves. Phased array technology harnesses the physics of constructive and destructive wave interference. In a phased array methodology, individual piezoelectric elements are excited in a controlled manner such that the direction of the combined wavefront is easily controllable without any physical movements or changes of the operator. The sound waves in a phased array pulse may be steered through a multitude of angles in a similar amount of time that a traditional A-scan flaw detector scans only a single angle. Scanning at many angles enhances the probability of finding defects in materials.
Although PAUT is often used in weld inspection, it has not found common use for inspection of raw tubular stock, particularly due to several shortcomings. Accordingly, it is desirable to provide a method and apparatus for phased array ultrasound testing of tubular goods and other mechanical equipment that overcomes such shortcomings so as to provide more effective and economical flaw detection.
3. Identification of Objects of the Invention
A primary object of the invention is to provide a method and apparatus for phased array ultrasound inspection of tubular goods that satisfies present A-scan inspection standards.
Another object of the invention is to provide a method and apparatus for effective calibration of phased array ultrasound inspection systems when used with tubular goods.